## Conductors and Insulators

Not all materials transfer energy the same way. A conductor is a material that allows thermal or electrical energy to pass through it easily. Metals such as copper, aluminum, and iron are excellent conductors of both heat and electricity. This is why cooking pots are made of metal (they conduct heat to the food) and electrical wires are made of copper (it conducts electricity efficiently).

An insulator is a material that resists the transfer of energy. Rubber, plastic, wood, air, and foam are good insulators. This is why pot handles are often made of wood or plastic (they insulate your hand from the hot metal), electrical wires are coated in rubber or plastic (to prevent the electricity from escaping), and winter coats trap air (which is an excellent thermal insulator).

## Electrical Circuits

For electrical energy to flow, it needs a complete, unbroken path called a circuit. A basic circuit has four components:

1. Energy source (battery or power supply) that pushes electrons through the circuit 2. Conductor (wire) that provides a path for the electrons to travel 3. Load (light bulb, motor, or speaker) that uses the electrical energy to do work 4. Switch (optional) that can open or close the circuit to control the flow

When the circuit is closed (all connections are complete), electric current flows and the load works. When the circuit is open (there is a break anywhere in the loop), current stops and the load turns off.